This invention pertains to an apparatus for printing on compressible material, such as corrugated board, without producing any distorting compression on the compressible material so as to produce thereon a clear cut printing on the material.
As far as I am aware, the art is devoid of any showing of a relatively simple adaptation of the conventional lithographic printing means to printing on compressible material without any distortion thereof.
In the conventional printing apparatus, a drive cylinder is provided, a printing blanket is provided, as well as a metallic impression cylinder and what is normally called an offset cylinder. All of these cylinders are of noncompressible material, such as metal, and would if used in a conventional manner on compressible material, compress and distort the compressible material upon which the printing is being transferred.
It is essential in printing, of the character in which I am particularly interested, and wherein a printing blanket of rubber is used, to provide two cylinders of noncompressible material, one of which carries the printing plates and is adapted to transfer the image from such plates to the blanket, and in order to produce a clear cut image on the blanket, it is necessary that the two cylinders between which the blanket travels be of hard, noncompressible material. It has been my experience that it is not possible to produce a true and detailed image on a printing blanket unless each of the cylinders between which the blanket travels are of hard noncompressible material. Thus, it is to be appreciated that a true and detailed image would not be transferred from the printing plates to the blanket if one of these cylinders between which the blanket travels was provided with a soft or cushioning medium about the circumference thereof, the blanket being in contact therewith.